#include <iostream>

const double PI = 3.14;

class Circle
{
// 权限：public、private、protected
public:
    int m_r;  // 半径

    double calculataZC()
    {
        return 2 * PI * m_r;
    }
};

int main()
{
    // 创建圆的对象
    Circle c1;
    // 给圆的对象赋值
    c1.m_r = 10;
    std::cout << "圆的周长为：" << c1.calculataZC() << std::endl;
}